Plasma Corticosterone Response of Turkeys to Adrenocorticotropic Hormone: Age, Dose, and Route of Administration Effects ,

Three trials were conducted to investigate plasma corticosterone (B) levels in Large White turkey hens in response to adrenocorticotropic hormone (ACTH) injections at different ages, doses, and routes of administration. In Trial 1, hens were subjected to one of the following treatments at 10, 15, and 20 wk of age: cold water immersion (5 C for 1 min), ACTH injection (10 IU/kg), or saline injection. The plasma B responses to ACTH and cold water immersion followed the same general pattern in all three age groups. Plasma B levels of hens in the ACTH treatment were depressed below control B levels until 6 h postinjection, when they became elevated. Plasma B levels of hens in the cold water treatment were either similar to or increased above those of controls by 2 h posttreatment and were depressed below control levels at .5 h posttreatment at 10 and 15 wk of age. In Trial 2, three dose levels of ACTH (1, 5, and 10 IU/kg) were injected either intramuscularly (IM) or intravenously (IV) in 10-wk-old hens. There was both a dose and route of administration effect. Of the IM-injected hens, only those in the 1-IU ACTH treatment group had significantly (P<.05) increased plasma B levels and this occurred 4 h postinjection. However, plasma B levels of the 1 and 5-IU IV-ACTH treatment hens were significantly (P<.05) elevated at .5 h postinjection. Plasma B of the 10-IU IM and IV-ACTH treatments were consistently, but not significantly, lower than controls through 4 h postinjection. In Trial 3, IV-ACTH treatments of .1, .5, 1, and 2 IU/kg were injected in 10-wk-old hens. The B levels of .5, 1, and 2-IU ACTH treatments rose significantly (P<.05) above control values by 4 h and persisted to 16 h postinjection. The B levels of the .1-IU ACTH treatment increased between 15 min and 1 h postinjection and also persisted for 16 h. It was concluded that the dose, route of administration, and time after treatment, but not age, influenced the plasma B response to ACTH.